Filters, optical leakage

HEPA and ULPA filters have been developed. In the CEN EN 1822 1998 test method, the filter s efficiency is determined for the most penetrating particle size (MPPS). Depending on the filter s total level of separation and leakage, the filter is classified as HIO, Hll,.. ., H14 and U15, U16, or U17. HEPA filters are commonly used for inlet air in the pharmaceutical, optical, and food industries. 

The are two other important advantages of the X-ray excitation technique (a) Levels lying within the optical absorption band of the host may be excited and (b) filters are not required to eliminate leakage of the pumping radiation from the detector. 

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